Fuel oil compositions having improved pour properties



United States Patent 3,443,917 FUEL OIL COMPOSITIONS HAVING IMPROVED POUR PROPERTIES William M. Le Suer, Cleveland, Ohio, assignor to The BIIIPI'IZOI Corporation, Wicklilfe, Ohio, a corporation of IO No Drawing. Filed May 19, 1964, Ser. No. 368,742 Int. Cl. C101 1/18 US. Cl. 44-62 4 Claims ABSTRACT OF THE DISCLOSURE Fuel oil compositions incorporating interpolymers of ethylene and propylene have improved pour properties. The fuel oils present in these compositions have initial pour points above about -25 F. Interpolymers useful have a molecular weight of about 50,000-500,000, about 45 mole percent of propylene and about 55-80 mole percent of ethylene. These compositions provide for the process of operating a furnace on oil which is stored at low temperature.

The present invention relates to improved hydrocarbon fuel oil compositions. It relates more particularly to such compositions which have improved flow and pour properties.

The pour point of an oil is defined as the lowest temperature at which the oil will pour or flow when chilled without disturbance under specified conditions. The problems associated with pour point ordinarily have to do with the storage and use of heavy oils such as lubricating oils, but the recent increased use of distillate fuel oils have revealed similar problems even with these lighter, more fluid materials. Pour point problems arise through the formation of solid or semi-solid waxy particles in an oil composition. In the storage of furnace oils or diesel oils during the winter months, for example, temperatures may decrease to a point as low as ---15 to F. The decreased temperatures often cause crystallization and solidification of wax in the distillate fuel oil. Distribution of heating oils by pumping or syphoning is rendered difficult or impossible when temperatures are around or below the pour point of the oil. Furthermore, at such temperatures the flow of the oil through the filters cannot be maintained, and the result is a failure of the equipment to operate.

This difficulty has been remedied in some instances by using lighter fractions as fuel oils, i.e., by lowering the maximum distillation temperature at which a distillate fraction is collected. It has also been suggested that the distillate fuel oils be dewaxed such as by urea dewaxing. Separately or in combination, these remedies are, however, economically prohibitive. That is, readjustment of end points causes the loss of valuable blending material for distillate fuel stocks and dewaxing operations are expensive.

Another approach to the problem has involved a search for a pour point depressant which will decrease the pour point of the distillate fuel oil. Unfortunately, pour point depressants which are normally effective in lubricating oils and other heaving oils are generally ineffective in a distillate fuel oil.

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The principal object of this invention is, therefore, to provide a process for operating an oil furnace whereby the fuel to be burned therein is maintained in a fluid condition and susceptible to How when stored at low temperatures.

Another object of this invention is to provide fuel oil compositions having improved pour properties at low temperatures.

These and other objects are accomplished according to the present invention by providing an improved process for the operation of an oil furnace whereby a liquid hydrocarbon fuel having a pour point above about 25 F. is burned, the improvement comprising incorporating in said fuel from about 0.001 to about 2% by weight of a substantially amorphous interpolymer of ethylene and propylene, said interpolymer having a molecular weight of from about 50,000 to about 500,000, a propylene content of from about 20 to about 45 mole percent, and an ethylene content of from about 55 to about mole percent.

The molecular weight indicated above is calculated from the reduced specific viscosity of the interpolymer. This calculation is made using the following equation:

RS V=AM wherein RSV is the reduced specific viscosity, and M is the molecular weight; A is 0.000100 and x is 0.80 for polypropylene (Kirk-Othmer, Encyclopedia of Chemical Technology, 663 (2nd Supp. 1960) and A is 0.000677 and x is 0.67 for polyethylene (Gaylord and Mark, Linear and Stereoregular Addition Polymers, 79 (1959)). The values of A and x are obtained by linear interpolation between the above values for interpolymers of ethylene and propylene, based on the relative molar proportions of the monomers, e.g., for an interpolymer containing 30 mole percent of propylene and 70 mole percent of ethylene, A 's 0.000504 and x is 0.709.

The term reduced specific viscosity means the specific viscosity, corrected to zero shear gradient, divided by the concentration of the solution in grams per milliliters. The viscosity is measured at C. on a solution of interpolymer in decalin containing 0.1 grams of the interpolymer in 100 milliliters of the solution.

Interpolymers having molecular weights of from about 50,000 to about 500,000 are useful for the purposes of this invention. The indicated molecular weight range of from about 50,000 to about 500,000 corresponds to a range of reduced specific viscosity of from about 1 to about 3.5. The preferred molecular weight range is from about 80,000 to about 350,000 and this corresponds to a reduced specific viscosity range of from about 1.3 to about 2.6.

The interpolymers of this invention are derived principally from ethylene and propylene. These interpolymers may, however, include minor amounts, e.g., from about 1 to about 3 mole percent, of other monomers. Examples of these other monomers include materials having the general formula, RCH=CH wherein R is an alkyl radical containing from 2 to 8 carbon atoms. Examples of t% latter include butene-3, hexene-l, 4-met-hyl-l-pentene, and decene-l. The other monomer may also be a diolefin containing from 5 to 22 carbon atoms, e.g., 1,4-pentadiene,

3 1,5-hexadiene (biallyl), 2-methyl-1,5-hexadiene, 3,3- dimethyl-l, S-hexadiene, 1,7-octadiene, 1,9-decadiene, 1,19-eicosadiene, and dicyclopentadiene. Preferably, the interpolymers contain only ethylene and propylene units. Interpolymers containing from about 20 to about 45 mole percent of propylene and from about 55 to about 80 mole percent of ethylene are useful for the purposes of this invention. However, interpolymers containing from about 25 to about 40 mole percent of propylene and from about 60 to about 75 mole percent of ethylene are especially preferred.

The term substantially amorphous indicates that a certain degree of crystallinity in the interpolymer is permissible. Highly crystalline interpolymers are relatively insoluble in fuel oil, especially at lower temperatures. A simple procedure for determining the degree of crystallinity of the interpolymers consistsof dissolving a known quantity, e.g., 5 grams, of a given interpolymer in n-heptane (100 milliliters), the quantity of the insoluble proportion being taken as a measure of the degree of crystallinity. Interpolym'ers useful for the purposes of this invention should have no more than about 5% by weight of such insoluble proportion (in n-heptane) at C., and preferably, this insoluble proportion should total no more than about 3 by weight.

Amorphous interpolymers of the type described can be prepared by any of several methods known in the art. They can be prepared, for example, by copolymerizing ethylene and propylene under relatively mild conditions of temperature and pressure in the presence of a Ziegler type catalyst, viz, a mixture of a compound derived from a Group IV, V, or VI metal of the Periodic Table in combination with an organo metallic compound of a Group I, II, or 1H metal of the Periodic Table.

The Group IV-VI metals that are used as indicated include titanium, zirconium, halfnium, thorium, uranium, vanadium, niobium, tantalum chromium molybdenum, selenium, tellurium, and tungsten. Halides, oxychlorides, acteylacetonates, alcoholates, oxides, complex halides such as the fluorotitanates and fluoroziconates, acetates, and benzoates, of the indicated metals are useful components of the above-indicated catalyst system. The salts of titanium, zirconium, chromium, thorium, vanadium, and uranium are particularly effective. Examples of such compounds include titanium tetrachloride, titanium trichloride, titanium dichloride, tetrabutyl titanate, vanadium tetrachloride, vanaclyl trichloride, vanadium trichloride, vanadium triacetylacetonate, vanadium oxyacetylacetonate, zirconium tetrachloride, zirconium acetylacetonate, chromium acetylacetonate, etc.

Group I-III metals from which the organo metallic compound is derived include the alkali metals, the alkaline earth metals, zinc, and the rare earth metals. Examples of the organometallic compound include alkali metal alkyls or aryls such as butyllithium, amylsodium, phenylsodium, etc., dimethylmagnesium, diethylmagnesium, diethylzince, butylmagnesium chloride, phenylmagnesium bromide, alkylor aryl-aluminum compounds as, for example, triethylaluminum, tripropylaluminum, triisobutylaluminum, trihexylaluminum, trioctylaluminum, dimethylaluminum chloride, methyl aluminum dichloride, the equimolar mixture of the latter two, known as aluminum sesquichloride, dii'sobutylaluminum chloride or fluoride, etc., and complexes of such organo metallic compounds as, for example, sodium aluminum tetraethyl, lithium aluminum tetraoctyl, etc.

Effective catalyst combinations of the type described include in combination: aluminum triisobutyl and vanadyl trichloride; aluminum triisobutyl, aluminum chloride, and vanadyl trichloride; vanadium tetrachloride and aluminum trihexyl; vanadyl trichloride and aluminum trihexyl; vanadium triacetylacetonate and aluminum diethyl chloride; titanium tetrachloride and aluminum trihexyl; vanadium trichloride and aluminum trihexyl; titanium trichloride and aluminum trihexyl; titanium dichloride and aluminum trihexyl; etc'.'Most preferred are combinations of titanium and vanadium halides, oxyhalides or alcohol ates with lithium, sodium, magnesium and aluminum alkyls.

The polymerization usually is carried out by mixing the two catalyst components in a diluent such as a hydrocarbon solvent and then passing ethylene and propylene into the catalyst mixture at atmospheric or slightly elevated pressure and at room temperature or moderately elevated temperature.

Alternatively, the interpolymers can be prepared by the method described in Belgium Patent 535,082 wherein ingredients including ethylene and propylene are contacted with a catalyst containingas the essential ingredients an oxide of chromium associated with an oxide of silicon, aluminum, 'zirconium, or thorium. Such interpolymers may also be prepared by the methods described in US. 2,700,633, 2,792,288, and 2,726,231 in which the copolymerization of ethylene and.propylene is accomplished by bringing a mixture of the two compounds into contact with a subhexavalent moylbdenum-oxygen compound combined with an active alumina, titania, or zirconia support at a temperature between about 100 and 300 C., and a pressure between atmospheric and S000 p.s.1.g.

Because the monomers do notpolymerize at the same rate, i.e., ethylene polymerizes faster than propylene, the ratio of the starting mixture of monomer is not the same as that desired in the final product and this is, of course, a major consideration in the preparation of a particular final product. For example, the polymerization may be carried out in n-heptane 25 -65 C. under normal pressure and in the presence of a catalyst prepared by adding :vanadyl trichloride to aluminum trihexyl in a molar ratio of 1:3. Under these conditions, the starting mixture of monomers should comprise from about 25 to about 50 mole percent of ethylene and from about 50 to about 75 mole percent of propylene to obtain the interpolymers as described above, i.e., having a propylene content of from about 20 to about 45 mole percent and an ethylene content of from about 55 to about mole percent.

When the polymerization is carried out in a solvent, the production of amorphous interpolymer is favored. Often, an extraction with n-heptane will assure the amorphous quality of the interpolymer so that it meets the solubility requirements as aforesaid. Such an extraction is especially desirable where the interpolymer is not prepared in a solvent.

The following example is illustrative.

EXAMPLE Tetrachloroethylene (3 liters) is passed through a silica gel column, sparged with nitrogen and then added under nitrogen to a dry reaction flask at 25 C. Agitation is begun and an equimolar mixture of gaseous ethylene and propylene is introduced below the tetrachloroethylene liquid surfaceat a rate of milliliters per second until a saturated monomer solution is obtained, the excess gas being allowed to escape through a gas outlet tube. To this saturated monomer solution there is added 8 milliliters (0.0128 mole) of a 1.6 molar solution of aluminum triisobutyl in cyclohexane and 0.94 milliliters (0.010 mole) of vanadyl trichloride, separately and rapidly in turn, by means of syringes, through an opening in the reactor sealed with a soft rubber cap. The tetrachloroethylene solution turns a clear amber color and the temperature rises to about 40 C. after a minute. To the agitated reaction mixture at 3540 C., an equimolar mixture of gaseous ethylene and propylene is introduced at a rate of 300 milliliters per second over a period of 0.5 hour. To the reaction mixture there is added 5 milliliters of n-butanol contaming 0.5 gram of 2,2'methylene-bis(6-tert-butyl-4- methylphenol) and the ethylene-propylene feed stream is shut off. The reaction mixture is poured into 3 liters of n-butanol and the polymer separates as a rubbery swollen were obtained by the method described in ASTM D9757.

TABLE Ethylene-propylene interpolymer Pour point F.) or fuel oil htfwing an interploymer content Pro lene Content 1 Molecular (mo fe percent) RSV weight; 0. 01% 0. 02% 0. 025% 0. 03% 0. 04% 0. 05%

1 The balance of the interpolymer is ethylene.

mer thereby obtained has a propylene content of mole percent.

The fuel oils suitable for use in a burner include hydrocarbon oils such as distillate and residual burner oils and diesel fuels having the following characteristics: mini mum flash point, 80 F.; maximum pour point, 70 F.; maximum 10% point, 650 F.; maximum 90% point, 900 F.; minimum API gravity, 24; and maximum viscosity at 100 F., 130 SUS (Saybolt Universal Seconds). They may be derived from petroleum by a variety of methods including straight distillation from crude petroleum oil and thermal or catalytic cracking of petroleum oil fractions.

The fuel oil compositions of this invention may be prepared merely by dissolving the indicated interpolymers in an appropriate fuel oil at the desired level of concentration. Generally, depending upon the fuel oil used, such dissolution will require mixing and some heating. Mixing may be accomplished by any of the many commercial methods, ordinary tank stirrers being adequate. Heating is not absolutely necessary, but mild heating, e.g., at 25-95 C., will greatly accelerate dissolution. The amount of interpolymer incorporated may be from about 0.001 to about 2 percent by weight. The range of from about 0.01 to about 0.2 percent by weight is the preferred interpolymer concentration.

Alternatively, the interpolymers may be blended with suitable solvents to form concentrates that can be readily dissolved in the appropriate fuel oils at the desired concentrations. Fluid hydrocarbons such as kerosene, xylene, and mixtures of kerosene and xylene are used for this purpose. Although many solvents would be operable for this purpose, practical considerations involved in handling, such as flash point, must be considered. Since the concentrates may be subjected to cold temperatures, flow at these low temperatures is also a necessary consideration. Flow characteristics also are dependent upon the interpolymer and its concentration. A solution of an ethylene-propylene interpolymer at a concentration of less than about 20% by weight in xylene, kerosene or mixtures of xylene and kerosene meets all of the practical requirements. These solutions are prepared by stirring mixtures of the interpolymer and solvent, preferably at elevated temperatures for faster dissolution. Temperatures within the range of from about 90 to about 135 C. and up, but less than the solvent reflux temperature are suitable.

The data in the following table illustrates the pour point properties of the ethylene-propylene interpolymers utilized in the process of this invention. The fuel oil used in obtaining these results has a pour point of =10 F. and contains 70% by weight of a No. 2 distillate and by weight of kerosene. All pour points quoted hereafter In contrast to the illustrated interpolymers of this invention, polypropylenes in the indicated molecular Weight range, viz, 50,000-500,000, generally are soluble in fuel oil, but exhibit no pour point depressing properties at 0.01-0.50% by weight concentration. This is likewise true with respect to interpolymers of ethylene and propylene Which contain more than 45 mole percent of propylene. On the other hand, polyethylenes within the above molecular weight range are insoluble in fuel oils at low temperatures, e.g., polyethylene having a molecular weight of 100,000 is insoluble at 0.01% concentration in the above test fuel oil. Likewise, interpolymers of ethylene and propylene which contain more than 80 mole percent of ethylene are more crystalline than the interpolymers of this invention and tend to be insoluble.

What is claimed is:

1. A fuel oil composition consisting essentially of a liquid hydrocarbon fuel having a pour point above about 25 F. and from about 0.001 to about 2 percent by Weight of a substantially amorphous interpolymer of eth ylene and propylene having a molecular weight of from about 50,000 to about 500,000, a propylene content of from about 20 to about 45 mole percent, and an ethylene content of from about 55 to about 80 mole percent.

2. The composition of claim 1 wherein the interpolymer has a molecular weight of from about 80,000 to about 350,000.

3. The composition of claim 1 wherein the interpolymer has a propylene content of from about 25 to about 40 mole percent and an ethylene content of from about 60 to mole percent.

4. A fuel oil composition consisting essentially of a liquid hydrocarbon fuel having a pour point above about -25 F. and from about 0.01 to about 0.1 percent by weight of a substantially amorphous interpolymer of ethylene and propylene having a molecular weight of from about 80,000 to about 350,000, a propylene content of from about 25 to about 40 mole percent, and an ethylene content of from about 60 to about 75 mole percent.

References Cited UNITED STATES PATENTS 2,379,728 7/ 1945 Lieber et a1 44-62 XR 3,151,181 9/1964 Hewitt et al. 252-59 2,913,439 11/1959 Bondi et al. 44-70 3,082,192 3/ 1963 Kirshenbaum et al. 260-882 3,153,025 10/ 1964 Bush et al. 260-88.2 3,252,771 5/ 1966 Clough et al 44--62 DANIEL E. WYMAN, Primary Examiner. Y. H. SMITH, Assistant Examiner.

US. 01. X.R. 44 -so 

